1) Field of the Invention
This invention relates generally to fabrication of fuses in an integrated circuit structure. More particularly this invention relates to the formation of a fuse formed simultaneously with metal plugs of an interconnect structure and a guard ring structure.
2) Description of the Prior Art
Increasing metal levels for complex/powerful circuit functions are required for future semiconductor device designs. But it makes the redundancy technology of poly fuse by laser repairing very difficult due to too many oxides layers covering the fuse. Replacing the poly fuses with metal fuses is the simplest approach to overall overcome this barrier. Metal fuses with laser cuts would be preferred by industry but there are problems with fuse reliability. The inventors have found that metal corrosion, especially with fuses formed of Al, is a major issue for metal fuses with the same passivation scheme. Also it is difficult to control the thickness of oxide overlying fuses so to adequately cut the fuse with a laser.
FIG. 8 shows a cross section view of a conventional metal fuse 120. Polysilicon lines 104 are formed over a substrate 100 including a field oxide region. An interlevel dielectric (ILD) layer 108 is formed over the poly lines 104. Contact openings are formed in the IDL layer 108 and a first plug 110 is formed contacting the poly lines 104. Next a first metal layer 112 (M1) is formed over the first plug 110. The metal layer also is formed in device areas comprising metal lines (M1). Next, a first inter metal dielectric (MID) layer 114 having first via opening is formed. The via openings are filled with a second plug 124. Next, a metal fuse 120 is formed over the first inter metal dielectric (M0) layer and metal lines (M2) are simultaneous formed in device areas. The metal lines (M2) and the metal fuse are often formed of aluminum alloys or Al-Cu alloys. Next, insulating and passivation layers 124 are formed thereover. A fuse opening 126 is etched in the insulating and passivation layers 124.
The inventor has found a major corrosion problem 130 with this metal fuse 120 and the interconnect structure having the metal layer (e.g., 112) and plugs 108 124. The inventors have found corrosion 130 where the metals 112 120 contact the plugs 108, 124. It is the intent this patent to overcome this corrosion 130 problem.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering U.S. Pat. No. 5,472,901 (Kapoor) shows a process for making a metal fuse.
U.S. Pat. No. 5,618,750 (Fakuhara) shows a fuse structure with the fuse formed from the conventional metal layers.
U.S. Pat No. 5,573,970 (Pramanik) shows a method of forming an anti-fuse using a W-plug.
U.S. Pat. No. 5,538,924 (Chen) shows a fuse with guard ring. U.S. Pat No. 5,512,102 (Iranmanesh et al) shows a metal vertical fuse. U.S. Pat. No. 5,244,836 (Lim) shows a metal fuse. U.S. Pat. No. 5,427,979 (Chang) shows a multi-level fuse using plugs.
U.S. Pat. No. 5,472,901 (Kapoor ) shows another method from forming fuses 86 formed of Via plug metal 80.